1 Technical Field
The present invention relates to a carton blank and a carton which is to be filled with a consumable product accessible through an opening in the carton. More particularly, the invention pertains to an opening feature formed in a top panel of a microwavable carton which provides a reliable and consistent opening when opened by the consumer.
2. Background Art
Paperboard cartons have been manufactured with a variety of opening features which allow the consumer access to the contents of the cartons and which are microwavable in nature. These opening features may consist of perforations, herringbone cuts, adhesive weaknesses, as well as other means for providing a point along the top panel, side panel or hinge lines where the carton may be most readily opened. A further opening feature commonly employed in cartons of this type is that of double-cut scores, as shown in U.S. Pat. No. 3,399,820 issued to Foster et al.
The above mentioned opening feature is formed by way of double-cut scores, i.e. an inner and outer cut in the paperboard which extend approximately half way through the paperboard thickness and which runs substantially parallel to one another. By so providing these cut score lines, when the consumer applies an upward force or opening force on the pull tab provided between the pairs of cut score lines, a ply-separation occurs in the regions between the inner and outer cut score lines. Continued pulling of the pull tabs causes complete separation of the opening flap to allow the consumer unobstructed access to the contents of the container.
Similar opening features are disclosed in U.S. Pat. No. 4,746,109 issued to Prater and U.S. Pat. No. 4,613,046 issued to Kuckenbecker. As in the above-mentioned patent, a point of weakness is provided in a panel of a respective carton where a ply-separation of the panel is permitted to occur when the consumer applies an opening force to the pull tab. The ply-separation occurs between the two pairs of reverse cut score lines which are formed approximately half way through the panel of the carton. However, when forming the paperboard blanks which are to be later used in erecting the cartons disclosed, it is extremely difficult to accurately achieve the desired extent of the cut lines of both the top and bottom cut. These paperboard blanks are formed in a matrix which consist of a plurality of forming dies and counters. Because the paperboard material must be cut partially through both sides of the top panel in substantial alignment with one another to form the double or reverse cuts, an extensive alignment procedure must be undertaken to assure that each cut formed in each side of the paperboard blank of the matrix is properly formed.
U.S. Pat. No. 4,687,104 issued to Ielmini discloses a similar carton and carton blank having score lines formed in the outer and inner surfaces of the top and front flap. These score lines are referred to as extending partially through the outer and inner surfaces of the carton and carton blank, this being essentially identical to that disclosed in the above mentioned patents. Additionally, with the patent to Ielmini as well as those previously discussed, during the sealing of the front flap to the underlying side wall, often the pull tab of the lift tab of the front flap becomes inadvertently adhered to the underlying panel and consequently requires extensive effort on the part of the consumer to initiate the opening of the container.
Similarly, U.S. Pat. No. 4,594,492 issued to Maroszek discloses a carton having an opening feature formed in the top panel thereof and extending into the front flap forming a lift tab which includes a pull tab. Again the opening feature is defined by a pair of substantially parallel inner and outer partially cut lines of weakness, thus exhibiting a ply-separation therebetween during the application of an opening force by the consumer. In order to aid in the ply-separation, the outer line of weakness is formed substantially co-linear with the respective fold lines between the top panel and the side panels of the carton. In doing so, stress concentrations may be readily formed along this line of weakness. Also as with the previously discussed prior art references, during the sealing of the front flap to the underlying sidewall, the pull tab of the lift tab which is integrally formed within the front flap may be inadvertently adhered to the underlying panel resulting in a significant effort being required by the consumer to lift the lift tab and subsequently open the carton. It should be noted that by providing a partially cut score line of weakness substantially co-linear with the fold line between the top panel and side panels thereof, may result in these edges being easily worn in that the outer coating of the paperboard material will be severed along substantially the entire length of the fold line. Such may result in an unsightly appearance of the container after a minimal amount of handling.
In an effort to overcome the above-mentioned shortcomings associated with the prior art, U.S. Pat. No. 4,886,170 and No. 4,919,785 issued to Wiley et al. disclose cartons similar to those discussed above. The opening feature of Wiley et al. includes inner and outer partially cut score lines as with the previous references however, the portion of the outer cut score line which extends substantially co-linear with the fold line between the top panel and the side panel is formed in a non-continuous manner thereby leaving a portion of the outer surface of the paperboard material intact about the respective fold lines. However, as with the previous references, the formation of partially cut score inner and outer lines of weakness in the paperboard material is difficult to control and with a portion of the inner and outer cut score line of weakness being formed in a non-continuous manner only adds to the difficulty in forming such lines of weakness. In addition to the foregoing, as previously discussed, during the sealing of the carton, the pull tab extension of the lift tab integrally formed in the front flap may be inadvertently sealed to the underlying panel. If such is the case, a ply-separation may occur in undesirable regions of the front flap during the application of an opening force to the lift tab by the consumer.
As can be seen from the foregoing, there is clearly a pressing need for a carton of the above-mentioned type which will provide a reliable and easy opening feature that is capable of being opened with ease by the consumer, and which may be readily and reliably formed during the manufacture of the paperboard blanks.